A balun is a type of transforming device that acts as an adaptor between devices that are configured for balanced, differential lines and devices that are configured for unbalanced, single-ended lines. As shown in FIG. 1A, a balun 10 receives an unbalanced, single-ended signal on line 12 with respect to ground and converts it into a balanced, differential signal on lines 14.
In FIG. 1B, baluns 10A, 10B are provided between a vector network analyzer (VNA) 16 and a device 18, such as a differential amplifier. VNA 16 is configured for unbalanced, single-ended lines, while device 18 is configured for balanced, differential lines. The first balun 10A converts the single-ended, unbalanced line from VNA 16 into balanced, differential lines for device 18 and the second balun 10B converts the balanced, differential lines from device 18 into a single-ended, unbalanced line for VNA 16.
The Marchand balun is one of the most commonly used baluns with a broad bandwidth. A standard Marchand balun can reach a bandwidth of approximately 80% to 100% of the center operating frequency.